Battle of Shimen

The Battle of Shimen occurred in 291 AD when the army of Sima Zhi attacked the invading army of Sima Yue in Pengcheng Commandery. Sima Yue had recently captured the temple at Pengcheng before marching south towards the town itself, but he was met halfway by Sima Zhi's army. In the ensuing battle, Sima Yue's army destroyed Sima Zhi's force and slew the rival prince, and Zhi Pingwen took over Sima Zhi's lands.

Background
In 291 AD, in retaliation for the rival prince Sima Zhi's invasion of Donghai Commandery, Prince Sima Yue captured the farming town of Lanling and marched deeper into Pengcheng Commandery with his army. In the autumn of 291 AD, the 953-strong army of Sima Yue took the temple of Pengcheng with 188 losses, leaving only the town of Pengcheng itself in Sima Zhi's hands. Sima Yue and his army then marched to the southern border of the county, where they encamped; they remained in friendly territory so that they could replenish their numbers. However, Sima Zhi marched north with a smaller army to confront Sima Yue's larger force, fighting out of range of the Pengcheng garrison's reach.

Battle
The battle began as the cavalry of the two armies clashed on the flanks, and Sima Yue led his infantry in standing firm as Sima Zhi's force assaulted their lines. Sima Yue and his general He Lun tracked down and killed both Sima Zhi and his prince Bao Xiangru, with Bao Xiangru being slain as he attempted to flee, while Sima Zhi was killed in the thick of the melee fighting. Sima Yue then had his forces give chase to the rebels, replenishing their ranks with the captured. Sima Zhi's death led to Zhi Pingwen inheriting his lands and continuing the war with Sima Yue. During the spring of 292 AD, Sima Yue and his army marched south and took Pengcheng from Gui Yi and Si Minmeng with 320 losses, finishing off Sima Zhi's domain and conquering Pengcheng Commandery.

Aftermath
Sima Yue's conquest of Pengcheng Commandery gave him control of Xu Province, making him a powerful warlord. However, this also made him a threat to his neighbors Sima Wei (one of the most powerful of the "Eight Princes') and Sima Yao, who both declared war on him, leading to Sima Yue conquering additional lands out of self-defense.